Abstract: The preparation of ammonium uranyl gadolinium carbonate (AUGdC) using (NH₄)₂CO₃ solution from the mixed solution of UO₂(NO₃)₂ and Gd(NO₃)₃ by means of co-precipitation was investigated. The experiment shows that controlling the feed concentration in the range of 300-400 g/L and the volume ratio of (NH4)₂CO₃ and UO₂(NO₃)₂ solution in the range of 2.0-2.4 is feasible. The deoxidizing, pressing and sintering performances of preparated AUGdC powder are excellent. The sinter density of UO₂-Gd₂O₃ pellets is above 96%T.D.(theoretical density), Gd and U distributing equally, forming the UO₂-Gd₂O₃ solid solution, the average grain size is above 18 μm.